The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An internal combustion engine of a vehicle generates drive torque through the combustion of an air/fuel mixture. More specifically, air is drawn into the engine and is mixed with fuel. The air/fuel mixture is compressed within a cylinder of the engine and is ignited. Combustion of the compressed air/fuel mixture reciprocally drives a piston within the cylinder. The piston, in turn, rotatably drives a crankshaft, which outputs drive torque to a driveline.
In some instances, such as when the vehicle is stopped, the engine idles at or near an idle speed. Fluctuations in the idle speed can cause vibrations. The fluctuations are caused by torque output differences between each of the cylinders of the engine. The differences in torque output may be related to a number of factors, such as an effective compression ratio, an air/fuel ratio, etc. The torque output differences between the cylinders tend to accentuate with increased age of the engine.
One method of controlling engine idle speed of the engine includes adjusting air and/or fuel flow to maintain a selected idle speed. This has limited control over maintaining an idle speed and in preventing fluctuations in torque output.